Masking apparatus for selectively charging honeycomb structures

ABSTRACT

Improved masking apparatus and methods for bulk charging a flowable material into selected cell ends exposed at an end face of a honeycomb structure. The masking apparatus utilize protrusions which assist in properly aligning the apparatus to the end face and reduce the possibility of improperly charging cells. In one apparatus embodiment, a planar body is provided having a plurality of hollow protrusions which extend into selected cell ends when the planar body is fitted against an end face of the structure. A flowable material charged against the planar body passes through the hollow protrusions into the selected cell ends. In another embodiment, a plurality of preformed protrusions or plugs are mounted along thin, flexible members at predetermined locations. The plugs are removably inserted into and temporarily block or cover the ends of an equal plurality of cells. A flowable material charged against the end face passes into the remaining, uncovered cells. The invention is of particular use in fabricating solid particulate filter bodies from ceramic-based honeycomb structures.

This application is a division of application Ser. No. 295,610, filedAug. 24, 1981, now U.S. Pat. No. 4,427,728.

BACKGROUND OF THE INVENTION

This invention relates to charging flowable materials into selectedcells of a honeycomb structure and, more particularly, to methods andrelated apparatus for selectively manifolding (i.e. plugging) cells of ahoneycomb structure for the fabrication of filter bodies and otherselectively selected honeycomb structures.

Honeycomb structures having transverse, cross-sectional cellulardensities of one-tenth to one hundred or more cells per squarecentimeter, especially when formed from ceramic materials, have severaluses, such as solid particulate filter bodies and stationary ;heatexchangers, which may require selected cells of the structure to beclosed or blocked by manifolding or other means at one or both of theirends.

A solid particulate filter body may be fabricated utilizing a honeycombstructure having a matrix of intersecting, thin, porous walls whichextend across and between two of its opposing open end faces and form alarge number of adjoining hollow passages or cells which also extendbetween and are open at the end faces. To form a filter, one end of eachof the cells is closed, a first subset of cells being closed at one endface and the remaining cells at the remaining end face, so that eithermay be used as the inlet or outlet end of the filter. A contaminatedfluid is brought under pressure to one face (i.e. the "inlet" face) andenters the filter bodies via the cells which are open at the inlet face(i.e. the "inlet" cells). Because the inlet cells are sealed at theremaining (i.e. "outlet") end face of the body, the contaminated fluidis forced through the thin, porous walls into adjoining cells which aresealed at the inlet face and open at the opposing "outlet" end face ofthe filter body (i.e. "outlet" cells). The solid particulate contaminantin the fluid which is too large to pass through the porous openings inthe walls is left behind and a cleansed fluid exits the outlet face ofthe filter body through the outlet cells for use.

Rodney Frost and Irwin Lachman describe and claim in a commonly assignedcopending application Ser. No. 165,646, filed July 3, 1980 and entitledFilter and Related Apparatus, a most efficient solid particulate filterbody formed from a honeycomb structure in which the cells are providedin transverse, cross-sectional densities between approximately one andone hundred cells per square centimeter with transverse, cross-sectionalgeometries having no internal angles less than thirty degrees, such assquares, rectangles, equilateral and certain other triangles, circles,certain elipses, etc. The cells are also arranged in mutually parallelrows and/or columns. Alternate cells at one end face are filled in acheckered or checkerboard pattern and the remaining alternate cells arefilled at the remaining end face of the structure in a reversed pattern.Thus formed, either end face of the filter body may be used as its inletor outlet face and each inlet cell shares common walls with onlyadjoining outlet cells, and vice versa. Other cellular cross-sectionalgeometries and other patterns of sealed cells may be employed tofabricate effective, although perhaps less efficient filter bodies thanthose of Frost and Lachman.

For the mass production of such filters, it is highly desirable to beable to block selected cell ends as rapidly and as inexpensively aspossible. The previously referred to application Ser. No. 165,646describes fabricating filter bodies by plugging the end of each cellindividually with a hand-held, single nozzle, air actuated sealing gun.The hand plugging of individual cells by this process is long andtedious and is not suited for the commercial production of such filterswhich may have thousands of cells to be selectively sealed. Theapplication Ser. No. 165,646 also postulates the use of a sealing gunmounting an array of sealant nozzles so that the plugging mixture may besimultaneously injected into a plurality or all of the alternate cellsat each end face of the honeycomb structure. However, a working model ofthis device is not known to exist for plugging honeycomb structureshaving the higher cell densities referred to.

An alternative approach to manifolding selected cells at an end face ofa honeycomb structure is described and claimed by Rodney Frost andRobert Paisley in another commonly assigned copending application Ser.No. 283,733, filed July 15, 1981 andentitled Method and Apparatus forSelectively Charging Honeycomb Structures, in which an open surface of ahoneycomb structure is covered by a mask having a number of openingsextending through it. Plugging material is charged against the outersurface of the mask and through its openings into the proximal open endsof cells opposite the openings. Frost and Paisley specifically describethe use of a rigid plate having a plurality of bores extending throughit which are spaced and sized to coincide with the open ends of theselected cells at the end face of a honeycomb structure when the plateis positioned against the end face in alignment with its bores oppositethe selected cells. Successful use of such an apparatus is dependentupon the ability to provide honeycomb structures having end facesconforming to the face of the masking apparatus so as to prevent gapstherebetween which would allow the sealing material to charge intoadjoining cells and to provide predetermined, undistorted positioning ofthe cells at the end face of the honeycomb structure for accurateregistration of the selected cells with the openings in the mask, again,to prevent possible charging of sealing material into adjoining cells.

In a related area, U.S. Pat. No. 4,041,591 describes alternate methodsof fabricating a multiple flow path body such as a stationary heatexchanger in which a honeycomb structure is provided having its cellsarranged in columns across its open end faces, an open end face of ahoneycomb structure is dipped into a flowable resist material and theresist material removed from selected columns by cutting it awaytogether with the common walls of the adjoining cells in the selectedcolumn or, alternatively, the walls between the adjoining cells of theselected columns are cut away at the open end face of the structurebefore dipping the end face into the flowable resist material, then theresist material is blown from the selected columns using compressed airdirected down the selected columns where the adjoining cell walls havebeen removed. The end face was thereafter dipped into a slurry of cementto form a sealed channel across each of the selected columns. Theremaining flowable resist material was subsequently removed by heating.Although these methods do not involve charging a permanent pluggingmaterial into cells as the purpose is to create channels across the endsof cells, sufficient plugging material could be provided to block thecell ends exposed by the cutting step. As the cross-sectional density ofcells in the honeycomb structure is increased, for example to improvethe efficiency of a filter body, the tolerances needed for the removalof adjoining cell walls required by these methods tighten. The problemis particularly heightened when the filter bodies are fabricated fromextruded ceramic or ceramic-based honeycomb structures as the presentstate of the ceramic extrusion art cannot provide perfectly parallelrows and/or columns of cells. Also, these methods requires the partialdestruction of adjoining cell walls and are entirely unsuited for thefabrication of filter bodies or other selectively sealed honeycombstructures where the cells are plugged in a checkered or other possiblealternating cell pattern at the end faces.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a method for selectivelybulk charging cells of a honeycomb structure with a flowable materialwhich is compatible with any desired pattern of cells selected to becharged.

It is yet another object of the invention to minimize the overspill ofsealing material when bulk charging selected cells of a honeycombstructure.

It is yet another object of the invention to provide a method ofselectively manifolding large numbers of cells of honeycomb structuresthat is more rapid and less expensive than hand filling individual cellends.

These and other objects are accomplished by providing masking apparatuscomprising at least one base member having a plurality of protrusionsextending therefrom which can be registered with and inserted into theopen ends of a subset of the cells at an open end face of a honeycombstructure. According to one aspect of the invention, a flowable materialmay be channeled into selected cells through hollow protrusions insertedinto the ends of the selected cells, minimizing the likelihood ofoverspill into adjoining cells not to be charged. In one embodiment, arigid member is provided with a plurality of hollow tubes extendingthrough it and protruding from one of its outer surfaces. The tubes arepositioned with respect to one another across the member and sized so asto coincide with and extend into the ends of selected cells of ahoneycomb structure when the member is fitted against an end face of thestructure. A flowable material charged against the opposing outer faceof the member which coverably seals the open ends of all but the subsetof selected cells and passes through the hollow protrusions and into allof the selected cells. According to another aspect of the invention, aflowable material may be charged into a selected subset of cells at anopen end face of a honeycomb structure by blocking the ends of theremaining cells with an equal plurality of preformed protrusions orplugs. A flowable material then charged into the end face of thestructure passes into the unblocked cells. In an embodiment of thisaspect of the invention, selected cells of a honeycomb structrure aretemporarily blocked at one of the structure's open end faces by suitablepreformed plugs, such as capped rivets, which are inserted into the endsof the cells not to be charged and coverably seal the ends of thesecells. A flowable material charged against the end face of the structurepasses into all of the uncovered cell ends. The plugs are transverselyaffixed to thin, elongated members, such as wires, at predetermninedintervals for ease of use. Either embodiment may be used to fabricatesolid particulate filter bodies from porous walled, honeycomb structuresor to fabricate other selectively plugged honeycomb bodies from porousor non-porous honeycomb structures.

DESCRIPTION OF THE DRAWINGS

The various aspects of the invention are better understood withreference to the accompanying drawings, in which:

FIGS. 1 and 1a depict a solid particulate filter body fabricated usingthe inventive methods and apparatus;

FIG. 2 depicts a honeycomb structure and first mask embodiment;

FIG. 3 depicts in a sectioned, profile view, the mask embodiment of FIG.2 fitted to the honeycomb structure;

FIG. 4 depicts a flowable material being charged through one of thehollow protrusions of the mask embodiment of FIGS. 2 and 3 into a cellof the honeycomb structure;

FIG. 5 depicts a press apparatus for using the several mask embodimentsof FIGS. 2 through 4 and 6 through 7b;

FIG. 6 depicts a second mask embodiment of the invention being fitted toan end face of a honeycomb;

FIG. 6a depicts a thin flexible member and preformed plugs of FIG. 6 inan expanded view;

FIG. 6b is an expanded, sectioned, view of area 6b of FIG. 6 depictingthe covering of the open ends of some of the cells by individual plugmembers and their protrusion into the cell ends;

FIG. 6c is an expanded end view of the area 6c of FIG. 6 showing thearrangement of plug elements in alternate cells of the honeycombstructure exposing the remaining cells in the checkered pattern forfilling;

FIG. 7 depicts a preferred embodiment of the invention, an elastic mask,and a honeycomb structure with which it is used;

FIG. 7a is a view of the downstream face of the mask embodiment of FIG.7 along the lines 7a--7a depicting the relative positioning of some ofits protrusions and openings; and

FIG. 7b depicts in a cross-section profile view along the lines 7b--7bof FIG. 7, the preferred mask embodiment fitted to the honeycombstructure.

DETAILED DESCRIPTION OF THE INVENTION

A preferred use of each of the embodiments of the present invention isthe fabrication of solid particulate filter bodies as are described byFrost and Lachman in aforesaid copending application Ser. No. 165,646which is incorporated in its entirety by reference herein. An exemplarypreferred filter body of that invention is depicted in FIG. 1 and in across-sectioned view along the line 1a--1a in FIG. 1a. The filter bodycomprises a honeycomb structure 10 having a multiplicity of hollow, openended passages or cells 11 which typically extend in an essentiallymutually parallel fashion through the structure 10 so as to reduce backpressure in the filter body being fabricated. The ends of the cells 11are open at and form a pair of substantially identical open outersurfaces at end faces 12 and 13 of the structure. The cells 11 arethemselves formed by a matrix of intersecting walls 14 which extendbetween each of the end faces 12 and 13. For filter body applications,the walls 14 are porous nd continuous across the end faces 12 and 13 andpreferably uniformly thin, although walls of non-uniform thickness maybe used with less efficiency. A thicker, outer "skin" 15 may be beprovided around the cells 11 and thin walls 14 between the end faces 12and 13.

Honeycomb structures for solid particulate filtering and otherapplications may be formed from a variety of porous materials includingceramics, glass-ceramics, glasses, metals, cermets, resins or organicpolymers, papers, or textile fabrics (with or without fillers, etc.),and various combinations thereof and by variety of methods dependingupon the material (s) selected. Honeycomb structures having thenecessary uniformly thin, porous and interconnected walls for solidparticulate filtering applications are preferably fabricated fromplastically formable and sinterable, finely divided particles and/orshort length fibers of substances that yield a porous, sintered materialafter being fired to affect their sintering, especially metallicpowders, ceramics, glass-ceramics, cermets, and other ceramic-basesmixtures. An extruded ceramic honeycomb structure having cordierite asits primary crystal phase, which is preferred for moderately hightemperature solid particulate filtering applications (1,000° Centigradeor more) due to its low thermal expansion characteristics, may beprovided in the manner described in the aforementioned Frost and Lachmanapplication Ser. no. 165,646. Several exemmplary raw material mixturesare described therein which yield honeycomb structures with thin wallshaving various open porosities. The filter body is formed by plugging,covering or otherwise blocking the ends of a subset of alternative cellsat one end face of the structure and the remaining cells at theremaining end face of the structure. In FIGS. 1 and 1a, alternate cells11 of the honeycomb structure 10 have been blocked with plugs 16 ateither end face in a checked or checkerboard pattern described andclaimed in the aforesaid application Ser. No. 165,646. The pluggingpattern on the end face 13 (hidden in FIG. 1) is the reverse of thatdepicted on the end face 12. Further information regarding the use andoperation of the described filter bodies is provided in the aforesaidapplication Ser. No. 165,646. The plugs 16 are selected from a materialcompatible with the composition of the honeycomb structure and itsultimate use as a filter body. Where the aforesaid cordierite structuresare used for filtering applications, cordierite cement plugs 16 arepreferably provided for compatibility. Suitable foaming cordieritecements are described and claimed in application Ser. No. 165,647filedJuly 3, 1980 and entitled Ceramic Foam Cement, which is now U.S. Pat.No. Re 31,405 and incorporated by by reference herein. A particularcomposition of that cement preferred for high sodium ion exhaust gasfiltering applications is provided in the aforesaid application Ser. No.165,646. Non-foaming cordierite cement compositions which may be usedwith the porous walled cordierite substrates identified in theapplication Ser. No. 165,646 are identified in yet another copendingapplication Ser. No. 295,612 filed Aug. 24, 1981 entitled SelectivelyPlugged Sinterable Honeycomb Structures, now U.S. Pat. No. 4,455,180which is incorporated by reference herein. Alternatively, other ceramiccements and other plugging materials may be used with cordierite orother honeycomb structures to fabricate filter bodies and otherselectively plugged honeycomb structures using the subject inventionwhich is hereinafter described in three embodiments, including apreferred embodiment, in the context of fabricating the described solidparticulate filter bodies.

FIRST EMBODIMENT

FIG. 2 depicts a honeycomb structure 10 again having cells 11 formed bythin walls 14 extending between end faces 12 and 13 with a firstembodiment mask 20 of the subject invention. The mask 20 comprises arigid, essentially plate-like body 21 having opposing upstream anddownstream faces 22 and 23. The body 21, as shown in FIGS. 3 and 4, hasa plurality of bores 21a extending axially between its surfaces 22 and23 each of which is fitted with a hollow tube 24 which protrudes like anipple from the downstream surface 23 of the mask body 21. The mask 20is used by positioning its downstream face 23 against an end facae 12(or 13) of the structure 10 as indicated by the arrows 25 in FIG. 2,preferably until the downstream surface 23 is substantially flush withthe end face 12 (or 13) as is depicted in FIG. 3. The tubes 24 arepositioned with respect to one another across the mask body 21 and sizedso as to coincide with and extend into the ends of selected cells whenthe mask 20 is fitted to the end face 12 (or 13) of the structure 10. Asuitably flowable material (indicated by shading in FIG. 4), such as oneof the aforesaid ceramic plugging cements, which is charged against theupstream face 22 of the mask 20 under pressure, passes through the tubes24, as is indicated by the arrows 26 in FIG. 4, into the ends of theselected cells into which each tube 24 extends. Desirably, the outersurface of protruding nipples of tubes 24 taper inwardly as they extendfrom the plate-like body 21 so as to present a smaller transversecross-sectional area at their tip for easier registration with the opencell ends. The base of the nipples may be sufficiently wide so as torest on or fit snugly into the ends of the selected cells 11 to preventthe flowable plugging material from spilling or oozing over intoadjacent cells which are to remain open or unplugged. The mask 20 may bemade from metal components by assembly, in the manner described, ormonolitically by such methods as casting, or alternatively, from otherformable or machinable rigid materials. It is also envisioned that themask may be formed monolithically from a flexible or elastic polymermaterial in a manner similar to the preferred embodiment subsequentlydescribed herein.

FIG. 5 depicts an exemplary press apparatus 30 which may be used withthe first embodiment mask 20 to charge a plastically formable cement orother viscous material into selected cell ends of a honeycomb structure.The apparatus 30 comprises a press held 31 housing a piston 32 travelingin a bore 33 which is open at an outer surface 31a of the head 31 andadditional frame members 34 supporting a hand-operated screw 35 or othersuitable means for moving the piston 32 in the bore 33. A honeycombstructure 10 is charged using the mask embodiment 20 and the subjectpress apparatus 30 by withdrawing the piston 32 into the chamber 33forming a cavity between its head 32a and the outer surface 31a of thepress head 31. The ceramic cement or other material to be charged intothe structure 10 is loaded into the cavity. The honeycomb structure 10with fitted mask 20 is applied over the bore 33 and against the surface31a of the press head. The structure 10 and mask 20 are held in positionby suitable means such as a bar 36 positioned over the opposing end face13 of the structure, which bar is held in position by suitable meanssuch as threaded bolts 37 extending into suitably threaded bores 38 inthe press head 31. The piston 32 is then advanced towards the mask 20 bymeans of the screw 35 and presses the material in the cavity through thetubes 24 into the proximal ends of the cells 11 forming plugs 16. Plugs16a have been formed in the remaining alternate cells of the structure10 at the opposite end face 13 in a similar, previous filling operation.The structure 10 is then removed from the press head and the plugs 16and 16a fixed in position by sintering in the case of the aforesaidcordierite cements or by drying, curing or other appropriate steps forother plugging materials.

SECOND EMBODIMENT

FIGS. 6 through 6c depict a second embodiment of the inventioncomprising a multiplicity of preformed plug elements 40, each of whichis inserted into and blocks or covers the open end of a cell 11 at anend face 12 (or 13) of a honeycomb structure 10. For convenience, theplugging elements 40 are preferably prepositioned along elongatedmembers 41, such as flexible wires, which are sufficiently thin (i.e. ofwidth perpendicular to the axes of members 40 smaller than width ofcells) so as to not overlap or substantially block cells adjoining thosetemporarily plugged with the members 40. The flexible members 41 assistconsiderably the use of the plug elements 40. The flexibility of themembers 41 allows some latitude in aligning the plug elements 40 withdistorted arrangements of cells at an end face. The members 41 alsolocate the plug elements 40 in the vicinity of the appropriate cell endsduring insertion and provide a means for quickly removing the plugsafter the selected cells of the structure have been charged. Eachelement 40 has a central body portion 40a which is sufficiently small indiameter so as to be inserted into an open end of a cell 11.Additionally, each plug element 40 is provided with a larger headportion 40b having a diameter greater than the minimum diameter or widthof the open, transverse, cross-sectional areas of the cells. Headportion 40b both covers the cell ends preventing their charging andprevents the plugs 40 from being pushed completely past the end faceinto a cell end during the charging process. To plug alternate cells 11arranged in rows and columns at an end face 12 of a honeycomb structurein the aforementioned checkered or checkerboard pattern, flexibleelements 41 each carrying one or more plug elements 40 are arrangedalong alternate, parallel diagonals of cells at an end face, asindicated in FIG. 6c. The plug elements 40 may be inserted into thecells along the remaining alternate diagonals at the opposing end faceof the structure 10 to achieve the desired, reversed, checkered orcheckerboard plugging pattern. The flexible members 41 may be providedsufficiently long so as to overlap the sidewalls 15 of the structure 10where they may be held in place by suitable means 42 for the chargingmethods selected. For example, the press apparatus 30 of FIG. 5 may beused by stretch-fitting an oversized collar, such as an annular, hollowneoprene ring having an inner circumference slightly less than the outercircumference of the end face 12, over the end face 12 and onto thestructure sidewalls 15 and ends of the flexible members 41.Alternatively, an adjustable clamp, tape or other means may be used tosecure the ends of the flexible members 41 to the sides 15 of thestructure 10. A working model of the masking apparatus depicted wasfabricated by soldering small, copper rivets at predetermined locationsalong thin, copper wires. Although the depicted arrangement of theflexible members 41 along diagonals of cells arranged in rows andcolumns if preferred for the fabrication of solid particulate filterbodies having the preferred checked plugging pattern depicted in FIG. 1,it is envisioned that other plugging patterns can be achieved by otherspacings of the plugging elements 40 along the flexible members 41 andother orientations of the members 41 across an open end face of ahoneycomb structure 10.

PREFERRED EMBODIMENT

An embodiment of the invention which is preferred for fabricating solidparticulate filter bodies or for otherwise charging flowable materialsinto selected cells of honeycomb structures, in which the open ends ofthe cells or the arrangement of the cells across the end face may besomewhat distorted, is an elastic mask described and claimed in acopending application Ser. No. 283,734, filed July 15, 1981 and entitledMethod and Apparatus for High Speed Manifolding of Honeycomb Structures,now U.S. Pat. No. 4,411,856, which is incorporated by reference herein.An exemplary elastic mask 50 is depicted in FIGS. 7 through 7b togetherwith an exemplary honeycomb structure 10 with which it is used. The mask50 consists of a substantially plate-like body section 51 having aplurality of openings 52 extending substantially axially therethroughbetween an upstream face 53 and downstream face 54. A second pluralityof protrusions 55 is also provided extending in a substantially axialdirection from the downstream face 54. The openings 52 and protrusions55 are spaced with respect to one another and sized so as to coincidewith selected cells 11 when the mask is fitted to an end face 12 (or 13)of the structure 10. A portion of the openings 52 and protrusions 55 aredepicted in FIG. 7a in view of the downstream face 54 of the mask 50.The openings 52 and protrusions 55 are alternated with one another alongrows and columns parallel and perpendicular, respectively, to the line56 of FIG. 7a so as to coincide with alternate cells arranged in rowsand columns, respectively, at the end face 12 (or 13) of the structure10. The mask 50 is fitted to the end face 12 (or 13) of the structure10, as indicated by the arrows 57 in FIG. 7, with the downstream face 54flush against the ends of the cells 11, as depicted in FIG. 7b.Preferably, the protrusions 55 are also elastic and taper as they extendaway from the downstream face 54 from a cross-sectional diameter equalto or greater than a cross-sectional diameter less than the minimumdiameter of the open, cross-sectional area of the cell ends into whichthey protrude. The protrusions 55 assist in aligning the mask to the endface with its openings opposite the proper cell ends and temporarilyblock the cell ends into which they are inserted preventing the pluggingor other flowable material being charged through the mask 50 fromentering those cells. A more detailed description of the fabrication anduse of the mask 50 is provided in the aforesaid application Ser. No.283,734. A preferred embodiment for fitting the mask 50 to an end faceof a honeycomb structure is provided in yet another copendingapplication Ser. No. 283,735 filed July 15, 1981, entitled Method andApparatus for Aligning Body with Honeycomb Structure, which is assignedto the assignee of this application and is incorporated by referenceherein.

It will be appreciated that the described embodiments. are exemplary andthat variations and modifications may be made with respect to each. Forexample, although the first embodiment of FIGS. 2 through 4 was depictedin FIG. 5 with a press apparatus for charging a plastically formable orother highly viscous material into selected cell ends, it is envisionedthat the apparatus 20 may be used to charge less viscous materials suchas a plugging cement slurry into selected cell ends. One way toaccomplish this would be to position the honeycomb structure on its sidewith its end faces 12 and 13 in a vertical orientation. The apparatus 20is fitted to an end face in the manner described with its hollow tubesextending into the selected cell ends. A cement slurry is chargedagainst the upstream face 22 of the mask and injected through the hollowtubes 24 into the cell ends 11 while the mask 20 is slowly withdrawnfrom the end face 12 of the structure 10. The mask 20 would be withdrawnat the rate at about which the slurry is being deposited into the cellends. The flow of slurry would be halted just before the hollow tubes 24clear the end face of the structure 10. The structure 10 may be rolledor vibrated to assure distribution of the slurry across the cell end.Also, in accordance with Montierth's teaching in the aforesaidapplication Ser. No. 283,734, the plugs 40 of the second embodimentdepicted in FIGS. 6 through 6c may be made of a flexible or elasticmaterial and in a tapered configuration similar to the protrusions 55 ofthe mask embodiment of FIGS. 7 through 7b so as to conform to ortemporarily seal the cell ends into which they are inserted.

While particular embodiments of the present invention have been shownand described and some modifications suggested, it will be appreciatedthat other modifications of the invention, not specifically mentioned,will occur to those skilled in the art and are intended to be includedwithin the scope of the invention which is described in the appendedclaims.

What is claimed:
 1. The combination comprising:a honeycomb structurehaving a pair of opposing open end faces and a matrix of thin wallsdefining a multiplicity of hollow, open ended cells extending throughsaid structure between said pair of end faces, including a selectedsubset of said cells, and a plurality of preformed plugs for use in bulkcharging a flowable material into said selected subset of cells, each ofsaid preformed plugs removably inserted into and temporarilysubstantially blocking, at an end face, an open end of each of saidcells not in said subset.
 2. In a method of bulk charging a flowablematerial into a selected subset of cells of a honeycomb structure havinga pair of opposing open end faces and a matrix of thin walls defining amultiplicity of hollow, open ended cells extending through saidstructure between said pair of end faces, the improvement comprising thestep of:a removably inserting a preformed plug, at an end face, into andto temporarily substantially block an open end of each of said cells notin said subset.